Blood culture identification (BCID) performance in polymicrobial bacteremia

Area of Science:

• Clinical microbiology
• Infectious diseases
• Molecular diagnostics

Background:

• Rapid multiplex PCR (rmPCR)-based FilmArray® blood culture identification (BCID) assay significantly reduces time to organism identification from positive blood cultures.
• Polymicrobial bacteremia (PMB) presents a challenge to BCID assays, with known limitations in diagnostic accuracy that require further characterization.

Purpose of the Study:

• To evaluate the diagnostic performance of the FilmArray® BCID assay in cases of clinically confirmed polymicrobial bacteremia.
• To determine the frequency of incomplete organism identification in PMB using the FilmArray® BCID assay.

Main Methods:

• Retrospective cohort analysis of clinically confirmed PMB cases at a single academic center over 23 months.
• Evaluation of 207 samples identified and studied for complete or incomplete identification by the FilmArray® BCID assay.

Main Results:

• Nearly half (49.3%) of polymicrobial cultures were incompletely identified by the FilmArray® BCID assay.
• No significant differences were observed in patient comorbidities, length of stay, mortality, or infection source between groups with complete versus incomplete identification.
• The study highlights a frequent underestimation of microbial presence in PMB when using rmPCR-based assays.

Conclusions:

• rmPCR-based assays, such as FilmArray® BCID, frequently fail to identify all causative organisms in polymicrobial bacteremia.
• Clinical interpretation of FilmArray® BCID results in PMB cases should account for potential underidentification of pathogens.
• Further research may be needed to improve the sensitivity of molecular diagnostic tools for polymicrobial infections.